SEASONAL-VARIATIONS OF O-2, CO2, AND ETHYLENE IN OAK AND MAPLE STEMS

Oxygen, carbon dioxide, and ethylene in the outer sapwood of English oak (Quercus robur L.) and Norway maple (Acer platanoides L.) were monitored from May through September. Oxygen and carbon dioxide were measured by gas chromatography - mass spectrometry, and ethylene by gas chromatography. In both species, the level of ethylene increased when cambial growth resumed in early May, peaked in June, and thereafter decreased, reaching the springtime level in August. In contrast, the concentration of oxygen in both species was high when growth started, but subsequently decreased to a minimum of about 5% in July. Thereafter the oxygen concentration increased and in September attained the early spring level. In maple, the concentration of carbon dioxide was steady throughout the experimental period, except for a decrease in June. In oak, the carbon dioxide level increased after growth resumed and peaked in August. The seasonal patterns of change in ethylene, oxygen, and carbon dioxide resembled those observed in conifers. However, the amplitude of the seasonal variations in oxygen and carbon dioxide was less than that found in conifers, suggesting that the system for delivering oxygen and removing carbon dioxide is more effective in deciduous species than in conifers.